xROUTINE  RoutineName

This is a "procedure" or "gosub" in other languages.
The commands attached to this event will never be executed, unless called
by another event.

Say you define an xROUTINE with the name of "Hello" :

xROUTINE Hello

Then from another event in the program you can call this routine with :

GoSub GuiName Hello

The commands attached to xROUTINE "Hello" will be executed and when finished,
control will be returned to the command after "Gosub GuiName Hello"

Starting with V3.2, Routines can take/return  Arguments 

Arguments may be accesses as internal variables $$ARG.0 to $$ARG.5, or
even better, defined in the routine's definition line :

>  XROUTINE MyRoutine  Arg1 Arg2 SomeArgName Arg6